ATM switches are used for routing data packets or signals through an ATM network. The ATM switch has a number of ports which may be connected to a device, such as another ATM switch or a peripheral device such as a computer, a video feed device, or a telecommunications device, each of which has a standard interface unit with a device port which may transmit and receive data packets from an ATM switch port. An example of a typical ATM switch is the model ASX-200 from Fore Systems, Inc. of Warrendale, Pa., USA.
An ATM switch port consists of a receive and a transmit interface. Each ATM device that connects to the switch also has a transmit and a receive interface. These interfaces each have a high bandwidth; 25 Mbits/s and 155 Mbits/s are the current standard data rates. However, many peripheral devices have a data rate much lower than this. For example, a video feed may have a data rate of 2 Mbits/s. There may therefore be a great deal of bandwidth unutilized on each ATM switch port.
One way to make better use of the bandwidth is to devise a way to connect a number of ATM devices to a single ATM switch port. One known way is to use "stacking" devices such as the product sold under the registered trade mark "CellStack" by K-NET Ltd. of Odiham, Hampshire, UK. However, many so-called "stacks" use a proprietary interconnect technology with one device in the stack being nominated as the interface unit according to the standard network format. It may therefore not be possible to redeploy the stacked devices, for example to connect each device to a single ATM switch port.
Another solution to the problem of under utilized bandwidth is the so-called "backplane" or "chassis" based approach for interfacing a number of different device types to the same network interface. However, when purchasing a chassis solution the customer has to estimate the final size of a desired configuration. It is also possible that the chassis "slots" purchased may be incompatible with later interfaces developed by the manufacturer.